Apparatus for transmitting broadcast signal and method for transmitting broadcast signal using layered division multiplexing

ABSTRACT

A broadcast signal transmission apparatus and method using layered division multiplexing are disclosed. A broadcast signal transmission apparatus according to an embodiment of the present invention includes a combiner configured to generate a multiplexed signal by combining a core layer signal and an enhanced layer signal at different power levels; a power normalizer configured to reduce the power of the multiplexed signal to a power level corresponding to the core layer signal; a time interleaver configured to generate a time-interleaved signal by performing interleaving that is applied to both the core layer signal and the enhanced layer signal; a frame builder configured to generate a broadcast signal frame using the time-interleaved signal; and an orthogonal frequency division multiplexing (OFDM) transmitter configured to generate a pilot signal that is shared by a core layer corresponding to the core layer signal and an enhanced layer corresponding to the enhanced layer signal.

TECHNICAL FIELD

The present invention relates to broadcast signal transmission/receptiontechnology that is used in a broadcasting system and, more particularly,to a broadcast signal transmission/reception system thatmultiplexes/demultiplexes and then transmits/receives two or moresignals.

BACKGROUND ART

Bit-Interleaved Coded Modulation (BICM) is bandwidth-efficienttransmission technology, and is implemented in such a manner that anerror-correction coder, a bit-by-bit interleaver and a high-ordermodulator are combined with one another.

BICM can provide excellent performance using a simple structure becauseit uses a low-density parity check (LDPC) coder or a Turbo coder as theerror-correction coder. Furthermore, BICM can provide high-levelflexibility because it can select modulation order and the length andcode rate of an error correction code in various forms. Due to theseadvantages, BICM has been used in broadcasting standards, such as DVB-T2and DVB-NGH, and has a strong possibility of being used in othernext-generation broadcasting systems.

To support multiple services at the same time, multiplexing, i.e., theprocess of mixing a plurality of signals, is required. Of multiplexingtechniques, currently widely used techniques include Time DivisionMultiplexing (TDM) adapted to divide and use time resources andFrequency Division Multiplexing (FDM) adapted to divide and usefrequency resources. That is, TDM is a method of assigning time segmentsto respective services, and FDM is a technique for assigning frequencyresource segments to respective services and then using them. Recently,there is an urgent need for new multiplexing technology that isapplicable to a next generation broadcasting system and provides greaterflexibility and performance than TDM and FDM.

DISCLOSURE Technical Problem

An object of the present invention is to provide new signal multiplexingtechnology that is capable of providing greater flexibility andperformance than TDM and FDM.

Furthermore, an object of the present invention is to enable eachservice to use 100% of time and frequency resources while supportingmultiple services in a next generation broadcasting system at the sametime.

Furthermore, an object of the present invention is to efficientlymultiplex/demultiplex signals corresponding to two or more layers bycombining the signals at respective different power levels.

Technical Solution

In order to accomplish the above objects, the present invention providesa broadcast signal transmission apparatus, including: a combinerconfigured to generate a multiplexed signal by combining a core layersignal and an enhanced layer signal at different power levels; a powernormalizer configured to reduce the power of the multiplexed signal to apower level corresponding to the core layer signal; a time interleaverconfigured to generate a time-interleaved signal by performinginterleaving that is applied to both the core layer signal and theenhanced layer signal; a frame builder configured to generate abroadcast signal frame using the time-interleaved signal; and anorthogonal frequency division multiplexing (OFDM) transmitter configuredto generate a pilot signal that is shared by a core layer correspondingto the core layer signal and an enhanced layer corresponding to theenhanced layer signal.

In this case, the broadcast signal transmission apparatus may furtherinclude an injection level controller configured to generate apower-reduced enhanced layer signal by reducing the power of theenhanced layer signal. In this case, the combiner may generate themultiplexed signal by combining the core layer signal and thepower-reduced enhanced layer signal.

In this case, the broadcast signal transmission apparatus may furtherinclude an L1 signaling generation unit configured to generate L1signaling information including the injection level information of theinjection level controller.

In this case, the broadcast signal transmission apparatus may furtherinclude: a core layer Bit-Interleaved Coded Modulation (BICM) unitconfigured to correspond to the core layer signal; and an enhanced layerBICM unit configured to perform Bit-Interleaved Coded Modulation (BICM)encoding different from that of the core layer BICM unit.

In this case, the core layer BICM unit may have a lower bit rate thanthe enhanced layer BICM unit, and may be more robust than the enhancedlayer BICM unit.

In this case, the power normalizer may correspond to a normalizingfactor, and may reduce the power of the multiplexed signal by a level bywhich the power has been increased by the combiner.

In this case, the injection level controller may correspond to a scalingfactor. In this case, each of the normalizing factor and the scalingfactor may be a value that is larger than 0 and smaller than 1, thescaling factor may decrease as a reduction in power corresponding to theinjection level controller becomes larger, and the normalizing factormay increase as a reduction in power corresponding to the injectionlevel controller becomes larger.

In this case, the injection level controller may change an injectionlevel between 3.0 dB and 10.0 dB in steps of 0.5 dB.

In this case, the enhanced layer signal may correspond to enhanced layerdata that is restored based on cancellation corresponding to therestoration of core layer data corresponding to the core layer signal.

In this case, the core layer BICM unit may include: a core layer errorcorrection encoder configured to perform error correction encoding onthe core layer data; a core layer bit interleaver configured to performbit interleaving corresponding to the core layer data; and a core layersymbol mapper configured to perform modulation corresponding to the corelayer data.

In this case, the enhanced layer BICM unit may include: an enhancedlayer error correction encoder configured to perform error correctionencoding on the enhanced layer data; an enhanced layer bit interleaverconfigured to perform bit interleaving corresponding to the enhancedlayer data; and an enhanced layer symbol mapper configured to performmodulation corresponding to the enhanced layer data.

In this case, the enhanced layer error correction encoder may have ahigher code rate than the core layer error correction encoder, and theenhanced layer symbol mapper may be less robust than the core layersymbol mapper.

In this case, the combiner may combine one or more extension layersignals, having lower power levels than the core layer signal and theenhanced layer signal, with the core layer signal and the enhanced layersignal.

Furthermore, an embodiment of the present invention provides a broadcastsignal transmission method, including: generating a multiplexed signalby combining a core layer signal and an enhanced layer signal atdifferent power levels; reducing the power of the multiplexed signal toa power level corresponding to the core layer signal; generating atime-interleaved signal by performing interleaving that is applied toboth the core layer signal and the enhanced layer signal; generating abroadcast signal frame using the time-interleaved signal; and generatinga pilot signal that is shared by a core layer corresponding to the corelayer signal and an enhanced layer corresponding to the enhanced layersignal.

In this case, the broadcast signal transmission method may furtherinclude generating a power-reduced enhanced layer signal by reducing thepower of the enhanced layer signal. In this case, the combining mayinclude generating a multiplexed signal by combining the core layersignal and the power-reduced enhanced layer signal.

In this case, the broadcast signal transmission method may furtherinclude generating L1 signaling information including injection levelinformation.

In this case, the reducing the power of the multiplexed signal mayinclude reducing the power of the multiplexed signal by a level by whichthe power has been increased by the combining.

In this case, the generating a power-reduced enhanced layer signal mayinclude changing an injection level between 3.0 dB and 10.0 dB in stepsof 0.5 dB.

In this case, the combining may include combining one or more extensionlayer signals, having lower power levels than the core layer signal andthe enhanced layer signal, with the core layer signal and the enhancedlayer signal.

Advantageous Effects

According to the present invention, new signal multiplexing technologythat is capable of providing greater flexibility and performance thanTDM and FDM is provided.

Furthermore, according to the present invention, multiple services canbe supported in a next generation broadcasting system at the same time,and also each of the services can use 100% of time and frequencyresources.

Furthermore, according to the present invention, signals correspondingto two or more layers can be efficiently multiplexed/demultiplexed bycombining the signals at respective different power levels.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a broadcast signaltransmission/reception system according to an embodiment of the presentinvention;

FIG. 2 is an operation flowchart showing a broadcast signaltransmission/reception method according to an embodiment of the presentinvention;

FIG. 3 is a diagram showing an example of a transmission pilotarrangement;

FIG. 4 is a block diagram showing an example of the channel estimationunit included in the OFDM receiver shown in FIG. 1;

FIG. 5 is a block diagram showing another example of the channelestimation unit included in the OFDM receiver shown in FIG. 1;

FIG. 6 is a block diagram showing an example of the signal multiplexershown in FIG. 1;

FIG. 7 is a diagram showing an example of the structure of a broadcastsignal frame;

FIG. 8 is a block diagram showing another example of the signalmultiplexer shown in FIG. 1;

FIG. 9 is a block diagram showing an example of the signal demultiplexershown in FIG. 1;

FIG. 10 is a block diagram showing an example of the core layer BICMdecoder and the enhanced layer symbol extractor shown in FIG. 9;

FIG. 11 is a block diagram showing another example of the core layerBICM decoder and the enhanced layer symbol extractor shown in FIG. 9;

FIG. 12 is a block diagram showing still another example of the corelayer BICM decoder and the enhanced layer symbol extractor shown in FIG.9;

FIG. 13 is a block diagram showing another example of the signaldemultiplexer shown in FIG. 1;

FIG. 14 is a diagram showing an increase in power attributable to thecombination of a core layer signal and an enhanced layer signal; and

FIG. 15 is an operation flowchart showing a signal multiplexing methodaccording to an embodiment of the present invention.

MODE FOR INVENTION

The present invention will be described in detail below with referenceto the accompanying drawings. In the description, redundant descriptionsand descriptions of well-known functions and configurations that havebeen deemed to make the gist of the present invention unnecessarilyobscure will be omitted below. The embodiments of the present inventionare provided to fully describe the present invention to persons havingordinary knowledge in the art to which the present invention pertains.Accordingly, the shapes, sizes, etc. of components in the drawings maybe exaggerated to make the description obvious.

Preferred embodiments of the present invention are described in detailbelow with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a broadcast signaltransmission/reception system according to an embodiment of the presentinvention.

Referring to FIG. 1, a broadcast signal transmission/reception systemaccording to the embodiment of the present invention includes abroadcast signal transmission apparatus 110, a wireless channel 120, anda broadcast signal reception apparatus 130.

The broadcast signal transmission apparatus 110 includes a signalmultiplexer 111 for multiplexing core layer data and enhanced layerdata, and an OFDM transmitter 113.

The signal multiplexer 111 combines a core layer signal corresponding tocore layer data and an enhanced layer signal corresponding to enhancedlayer data at different power levels, and generates a multiplexed signalby performing interleaving that is applied to both the core layer signaland the enhanced layer signal. In this case, the signal multiplexer 111may generate a broadcast signal frame using a time-interleaved signaland L1 signaling information. In this case, the broadcast signal framemay be an ATSC 3.0 frame.

The OFDM transmitter 113 transmits the multiplexed signal using an OFDMcommunication method via an antenna 117, thereby allowing thetransmitted OFDM signal to be received via the antenna 137 of thebroadcast signal reception apparatus 130 over the wireless channel 120.

In this case, the OFDM transmitter 1130 may generate a pilot signal thatis shared by a core layer corresponding to the core layer signal and anenhanced layer corresponding to the enhanced layer signal.

The broadcast signal reception apparatus 130 includes an OFDM receiver133 and a signal demultiplexer 131. When the signal transmitted over thewireless channel 120 is received via the antenna 137, the OFDM receiver133 receives an OFDM signal via synchronization, channel estimation andequalization.

In this case, the OFDM receiver 133 may include a channel estimationunit configured to perform channel estimation. In this case, the channelestimation unit may provide channel gain or an SNR estimated value tothe signal demultiplexer.

The signal demultiplexer 131 restores the core layer data from thesignal received via the OFDM receiver 133 first, and then restores theenhanced layer data via cancellation corresponding to the restored corelayer data. In this case, the signal demultiplexer 131 may generate abroadcast signal frame first, may restore L1 signaling information fromthe broadcast signal frame, and may use the L1 signaling information forthe restoration of a data signal. In this case, the L1 signalinginformation may include injection level information, normalizing factorinformation, etc.

As will be described in detail later, the signal multiplexer 111 shownin FIG. 1 may include a combiner configured to generate a multiplexedsignal by combining a core layer signal and an enhanced layer signal atdifferent power levels; a power normalizer configured to reduce thepower of the multiplexed signal to a power level corresponding to thecore layer signal; a time interleaver configured to generate atime-interleaved signal by performing interleaving that is applied toboth the core layer signal and the enhanced layer signal; and a framebuilder configured to generate a broadcast signal frame using thetime-interleaved signal and L1 signaling information. In this case, thebroadcast signal transmission apparatus 110 shown in FIG. 1 may beviewed as including: a combiner configured to generate a multiplexedsignal by combining a core layer signal and an enhanced layer signal atdifferent power levels; a power normalizer configured to reduce thepower of the multiplexed signal to a power level corresponding to thecore layer signal; a time interleaver configured to generate atime-interleaved signal by performing interleaving that is applied toboth the core layer signal and the enhanced layer signal; a framebuilder configured to generate a broadcast signal frame using thetime-interleaved signal; and an OFDM transmitter configured to generatea pilot signal that is shared by a core layer corresponding to the corelayer signal and an enhanced layer corresponding to the enhanced layersignal.

As will be described in detail later, the signal demultiplexer shown inFIG. 1 may include a time deinterleaver configured to generate atime-deinterleaved signal by applying time deinterleaving to a receivedsignal; a de-normalizer configured to increase the power of the receivedsignal or the time-deinterleaved signal by a level corresponding to areduction in power by the power normalizer of the transmitter; a corelayer BICM decoder configured to restore core layer data from the signalpower-adjusted by the de-normalizer using any one or more of channelgain and an SNR estimated value; an enhanced layer symbol extractorconfigured to extract an enhanced layer signal by performingcancellation corresponding to the core layer data on the signalpower-adjusted by the de-normalizer using the output signal of the corelayer FEC decoder of the core layer BICM decoder; a de-injection levelcontroller configured to increase the power of the enhanced layer signalby a level corresponding to a reduction in power by the injection levelcontroller of the transmitter; and an enhanced layer BICM decoderconfigured to restore enhanced layer data from the output signal of thede-injection level controller using any one or more of the channel gainand the SNR estimated value. In this case, the broadcast signalreception apparatus 130 shown in FIG. 1 may be viewed as including: anOFDM receiver configured to generate a received signal by performing anyone or more of synchronization, channel estimation and equalization on atransmitted signal, and to generate any one or more of channel gain andan SNR estimated value; a time deinterleaver configured to generate atime-deinterleaved signal by applying time deinterleaving to thereceived signal; a de-normalizer configured to increase the power of thereceived signal or the time-deinterleaved signal by a levelcorresponding to a reduction in power by the power normalizer of thetransmitter; a core layer BICM decoder configured to restore core layerdata from the signal power-adjusted by the de-normalizer using any oneor more of channel gain and an SNR estimated value; an enhanced layersymbol extractor configured to extract an enhanced layer signal byperforming cancellation corresponding to the core layer data on thesignal power-adjusted by the de-normalizer using the output signal ofthe core layer FEC decoder of the core layer BICM decoder; ade-injection level controller configured to increase the power of theenhanced layer signal by a level corresponding to a reduction in powerby the injection level controller of the transmitter; and an enhancedlayer BICM decoder configured to restore enhanced layer data from theoutput signal of the de-injection level controller using any one or moreof the channel gain and the SNR estimated value.

Although not explicitly shown in FIG. 1, a broadcast signaltransmission/reception system according to an embodiment of the presentinvention may multiplex/demultiplex one or more pieces of extensionlayer data in addition to the core layer data and the enhanced layerdata. In this case, the extension layer data may be multiplexed at apower level lower than that of the core layer data and the enhancedlayer data. Furthermore, when two or more extension layers are included,the injection power level of a second extension layer may be lower thanthe injection power level of a first extension layer, and the injectionpower level of a third extension layer may be lower than the injectionpower level of the second extension layer.

FIG. 2 is an operation flowchart showing a broadcast signaltransmission/reception method according to an embodiment of the presentinvention.

Referring to FIG. 2, in the broadcast signal transmission/receptionmethod according to the embodiment of the present invention, a corelayer signal and an enhanced layer signal are combined at differentpower levels and then multiplexed at step S210.

In this case, the multiplexed signal generated at step S210 may includea data signal and L1 signaling information. In this case, the L1signaling information may include injection level information andnormalizing factor information.

Furthermore, in the broadcast signal transmission/reception methodaccording to the embodiment of the present invention, the multiplexedsignal is OFDM transmitted at step S220.

In this case, a pilot signal that is shared by a core layer and anenhanced layer may be generated at step S220.

Furthermore, in the broadcast signal transmission/reception methodaccording to the embodiment of the present invention, the transmittedsignal is OFDM received at step S230.

In this case, at step S230, synchronization, channel estimation andequalization may be performed.

In this case, any one or more of channel gain and an SNR estimated valuemay be generated at step S230.

Furthermore, in the broadcast signal transmission/reception methodaccording to the embodiment of the present invention, core layer data isrestored from the received signal at step S240.

Furthermore, in the broadcast signal transmission/reception methodaccording to the embodiment of the present invention, enhanced layerdata is restored via the cancellation of the core layer signal at stepS250.

In particular, steps S240 and S250 shown in FIG. 2 may correspond todemultiplexing operations corresponding to step S210.

As will be described in detail later, step S210 shown in FIG. 2 mayinclude generating a multiplexed signal by combining a core layer signaland an enhanced layer signal at different power levels; reducing thepower of the multiplexed signal to a power level corresponding to thecore layer signal; generating a time-interleaved signal by performinginterleaving that is applied to both the core layer signal and theenhanced layer signal; and generating a broadcast signal frame using thetime-interleaved signal.

In this case, the core layer corresponding to the core layer signal andthe enhanced layer corresponding to the enhanced layer signal may sharea pilot signal.

In this case, the broadcast signal transmission method of step S210 maybe viewed as including generating a multiplexed signal by combining acore layer signal and an enhanced layer signal at different powerlevels; reducing the power of the multiplexed signal to a power levelcorresponding to the core layer signal; generating a time-interleavedsignal by performing interleaving that is applied to both the core layersignal and the enhanced layer signal; generating a broadcast signalframe using the time-interleaved signal; and generating a pilot signalthat is shared by a core layer corresponding to the core layer signaland an enhanced layer corresponding to the enhanced layer signal.

As will be described in detail later, steps S240 and S250 shown in FIG.2 may include generating a time-deinterleaved signal by applying timedeinterleaving to a received signal; increasing the power of thereceived signal or the time-deinterleaved signal by a levelcorresponding to a reduction in power by the power normalizer of thetransmitter; restoring core layer data from the power-adjusted signalusing any one or more of channel gain and an SNR estimated value;extracting an enhanced layer signal by performing cancellationcorresponding to the core layer data on the power-adjusted signal;increasing the power of the enhanced layer signal by a levelcorresponding to a reduction in power by the injection level controllerof the transmitter; and restoring enhanced layer data from thepower-adjusted enhanced signal using any one or more of the channel gainand the SNR estimated value. In this case, a broadcast signal receptionmethod according to an embodiment of the present invention may be viewedas including: generating a received signal by performing any one or moreof synchronization, channel estimation and equalization on a transmittedsignal, and generating any one or more of channel gain and an SNRestimated value; generating a time-deinterleaved signal by applying timedeinterleaving to the received signal; increasing the power of thereceived signal or the time-deinterleaved signal by a levelcorresponding to a reduction in power by the power normalizer of thetransmitter; restoring core layer data from the power-adjusted signalusing any one or more of channel gain and an SNR estimated value;extracting an enhanced layer signal by performing cancellationcorresponding to the core layer data on the power-adjusted signal;increasing the power of the enhanced layer signal by a levelcorresponding to a reduction in power by the injection level controllerof the transmitter; and restoring enhanced layer data from thepower-adjusted enhanced layer signal using any one or more of thechannel gain and the SNR estimated value.

FIG. 3 is a diagram showing an example of a transmission pilotarrangement.

Referring to FIG. 3, it can be seen that in a Layered DivisionMultiplexing (LDM)-based broadcasting system, a transmitter assignstransmission pilot signals to subcarriers to support the channelestimation of a receiver.

In this case, pilot signals may be assigned to predetermined subcarriersby the OFDM transmitter shown in FIG. 1.

In the example shown in FIG. 3, LDM signals are assigned to datasubcarriers, and single pilot signals are assigned to pilot subcarriers.That is, a core layer and an enhanced layer share the same pilot signal.

Pilot signals may be assigned to subcarrier locations havingpredetermined intervals (time intervals and frequency intervals) in thetime and frequency domains. Alternately, pilot signals may besuccessively assigned to predetermined time or frequency locations inthe time and frequency domains.

In this case, the locations of subcarriers used for pilot signals arepredetermined, and are shared by a transmitter and the receiver.

FIG. 4 is a block diagram showing an example of the channel estimationunit included in the OFDM receiver shown in FIG. 1.

Referring to FIG. 4, the channel estimation unit includes a pilotextractor 41, an interpolator 43, a moving average filter 45, and a timedeinterleaver 47.

The pilot extractor 41 receives an FFT output for a received signal,extracts signal values corresponding to a pilot subcarrier, andcalculates channel gain for the corresponding pilot subcarrier.

In this case, the channel gain for the pilot subcarrier may be estimatedusing a least square (LS) method based on a pilot signal predeterminedbetween the transmitter and the receiver.

After the channel gain corresponding to the pilot subcarrier has beenobtained, the interpolator 43 performs interpolation using channel gainvalues corresponding to the pilot subcarrier in order to estimatechannel gain corresponding to a data subcarrier.

In this case, the interpolation may be performed using various methods,such as a linear interpolation, a minimum mean square error (MMSE)method, FFT-based interpolation, etc. Furthermore, when the FFT-basedinterpolation is applied, various techniques, such as a virtual pilotmethod, a time windowing method, etc., may be additionally applied.

The channel gain values estimated via the interpolation are averagedover a predetermined time by the moving average filter 45. The influenceof noise is reduced by averaging the channel gain values.

In this case, a time length over which the moving average filter 45performs the averaging may be fixed or vary depending on a receiveroperation channel environment.

The output value of the moving average filter 45 passes through the timedeinterleaver 47 before it is input to the symbol demappers of the BICMdecoders of a core layer and an enhanced layer. The time deinterleaverthat is applied to channel gain may be the same as the timedeinterleaver that is applied to a data symbol.

The finally estimated channel gain value may be input to the symboldemappers of the BICM decoders of the core layer and the enhanced layer,which will be described with reference to FIG. 9 later. As will bedescribed later, the channel gain value may be also input to the symboldemapper of the BICM decoder of an extension layer.

FIG. 5 is a block diagram showing another example of the channelestimation unit included in the OFDM receiver shown in FIG. 1.

Referring to FIG. 5, a channel estimation unit includes a pilotextractor 41, an interpolator 43, a moving average filter 45, a channelcompensator 51, and an SNR estimator 55.

When the channel estimation unit shown in FIG. 5 is used, input to thesymbol demapper of BICM may be the SNR estimated value of each layerrather than channel gain.

The pilot extractor 41, the interpolator 43 and the moving averagefilter 45 shown in FIG. 5 are the same as those described with referenceto FIG. 4.

The channel compensator 51 shown in FIG. 5 may equalize a received datasignal by compensating the received data signal using an estimatedchannel gain value. In this case, the channel compensator 51 maycompensate for channel gain by dividing the received data signal by theestimated channel gain value.

The channel-compensated output may be provided to a time deinterleaver,which will be described with reference to FIG. 9 later.

When the received data signal is equalized as shown in FIG. 5, thesymbol demappers of core layer BICM and enhanced layer BICM require theSNR values of the signal in order to perform LLR calculation.

The SNR estimator 55 shown in FIG. 5 calculates SNRs corresponding torespective layers from the FFT output value of the received signal, andprovides the calculated SNRs to the respective symbol demappers of thelayers.

Since the core layer includes not only noise but also the enhanced layeras interference signals, the SNR of the core layer is calculated in theform of the ratio of (the core layer signal) to (interference andnoise).

Furthermore, since the enhanced layer BICM is demodulated after the corelayer signal has been eliminated, the SNR of the enhanced layer iscalculated in the form of the ratio of (the enhanced layer signal) to(noise) while taking into account an insertion level.

The SNR estimator 55 may perform grouping on the estimated SNR values sothat the same SNR value can be assigned to adjacent subcarriers or timeintervals.

FIG. 6 is a block diagram showing an example of the signal multiplexershown in FIG. 1.

Referring to FIG. 6, a signal multiplexer according to an embodiment ofthe present invention may include a core layer BICM unit 310, anenhanced layer BICM unit 320, an injection level controller 330, acombiner 340, a power normalizer 345, and a time interleaver 350, an L1signaling generation unit 360, and a frame builder 370.

Generally, a BICM device includes an error correction encoder, a bitinterleaver, and a symbol mapper. Each of the core layer BICM unit 310and the enhanced layer BICM unit 320 shown in FIG. 6 may include anerror correction encoder, a bit interleaver, and a symbol mapper. Inparticular, each of the error correction encoders (the core layer FECencoder, and the enhanced layer FEC encoder) shown in FIG. 6 may beformed by connecting a BCH encoder and an LDPC encoder in series. Inthis case, the input of the error correction encoder is input to the BCHencoder, the output of the BCH encoder is input to the LDPC encoder, andthe output of the LDPC encoder may be the output of the error correctionencoder.

As shown in FIG. 6, core layer data and enhanced layer data pass throughrespective different BICM units, and are then combined by the combiner340. That is, the term “Layered Division Multiplexing (LDM)” used hereinmay refer to combining the pieces of data of a plurality of layers intoa single piece of data using differences in power and then transmittingthe combined data.

That is, the core layer data passes through the core layer BICM unit310, the enhanced layer data passes through the enhanced layer BICM unit320 and then the injection level controller 330, and the core layer dataand the enhanced layer data are combined by the combiner 340. In thiscase, the enhanced layer BICM unit 320 may perform BICM encodingdifferent from that of the core layer BICM unit 310. That is, theenhanced layer BICM unit 320 may perform higher bit rate errorcorrection encoding or symbol mapping than the core layer BICM unit 310.Furthermore, the enhanced layer BICM unit 320 may perform less robusterror correction encoding or symbol mapping than the core layer BICMunit 310.

For example, the combination of the core layer error correction encoderand the core layer symbol mapper may be more robust than the combinationof the enhanced layer error correction encoder and the enhanced layersymbol mapper.

In this case, the core layer error correction encoder may exhibit alower code rate than the enhanced layer error correction encoder. Inthis case, the enhanced layer symbol mapper may be less robust than thecore layer symbol mapper.

The combiner 340 may be viewed as functioning to combine the core layersignal and the enhanced layer signal at different power levels. In anembodiment, power level adjustment may be performed on the core layersignal rather than the enhanced layer signal. In this case, the power ofthe core layer signal may be adjusted to be higher than the power of theenhanced layer signal.

The core layer data may use forward error correction (FEC) code having alow code rate in order to perform robust reception, while the enhancedlayer data may use FEC code having a high code rate in order to achievea high data transmission rate.

That is, the core layer data may have a broader coverage than theenhanced layer data in the same reception environment.

The enhanced layer data having passed through the enhanced layer BICMunit 320 is adjusted in gain (or power) by the injection levelcontroller 330, and is combined with the core layer data by the combiner340.

That is, the injection level controller 330 generates a power-reducedenhanced layer signal by reducing the power of the enhanced layersignal. In this case, the magnitude of the signal adjusted by theinjection level controller 330 may be determined based on an injectionlevel. In this case, an injection level in the case where signal B isinserted into signal A may be defined by Equation 1 below:

$\begin{matrix}{{{Injection}\mspace{14mu} {level}\mspace{14mu} ({dB})} = {{- 10}\; {\log_{10}\left( \frac{{Signal}\mspace{14mu} {power}\mspace{14mu} {of}\mspace{14mu} B}{{Signal}\mspace{14mu} {power}\mspace{14mu} {of}\mspace{14mu} A} \right)}}} & (1)\end{matrix}$

For example, assuming that the injection level is 3 dB when the enhancedlayer signal is inserted into the core layer signal, Equation 1 meansthat the enhanced layer signal has power corresponding to half of thepower of the core layer signal.

In this case, the injection level controller 330 may adjust the powerlevel of the enhanced layer signal from 3.0 dB to 10.0 dB in steps of0.5 dB.

In general, transmission power that is assigned to the core layer ishigher than transmission power that is assigned to the enhanced layer,which enables the receiver to decode core layer data first.

In this case, the combiner 340 may be viewed as generating a multiplexedsignal by combining the core layer signal with the power-reducedenhanced layer signal.

The signal obtained by the combination of the combiner 340 is providedto the power normalizer 345 so that the power of the signal can bereduced by a power level corresponding to an increase in power caused bythe combination of the core layer signal and the enhanced layer signal,and then power adjustment is performed. That is, the power normalizer345 reduces the power of the signal, obtained by the multiplexing of thecombiner 340, to a power level corresponding to the core layer signal.Since the level of the combined signal is higher than the level of onelayer signal, the power normalizing of the power normalizer 345 isrequired in order to prevent amplitude clipping, etc. in the remainingportion of a broadcast signal transmission/reception system.

In this case, the power normalizer 345 may adjust the magnitude of thecombined signal to an appropriate value by multiplying the magnitude ofthe combined signal by the normalizing factor of Equation 2 below.Injection level information used to calculate Equation 2 below may betransferred to the power normalizer 345 via a signaling flow:

Normalizing factor=(√{square root over((1+10^(−Injection level(dB)/10))})⁻¹  (2)

Assuming that the power levels of the core layer signal and the enhancedlayer signal are normalized to 1 when an enhanced layer signal S_(E) isinjected into a core layer signal S_(C) at a preset injection level, acombined signal may be expressed by S_(C)+αS_(E).

In this case, α is scaling factors corresponding to various injectionlevels. That is, the injection level controller 330 may correspond tothe scaling factor.

For example, when the injection level of an enhanced layer is 3 dB, acombined signal may be expressed by

$S_{C} + {\sqrt{\frac{1}{2}}{S_{E}.}}$

Since the power of a combined signal (a multiplexed signal) increasescompared to a core layer signal, the power normalizer 345 needs tomitigate the increase in power.

The output of the power normalizer 345 may be expressed byβ(S_(C)+αS_(E)).

In this case, β is normalizing factors based on various injection levelsof the enhanced layer.

When the injection level of the enhanced layer is 3 dB, the power of thecombined signal is increased by 50% compared to that of the core layersignal. Accordingly, the output of the power normalizer 345 may beexpressed by

$\sqrt{\frac{2}{3}}{\left( {S_{C} + {\sqrt{\frac{1}{2}}S_{E}}} \right).}$

Table 1 below lists scaling factors α and normalizing factors β forvarious injection levels (CL: Core Layer, EL: Enhanced Layer). Therelationships among the injection level, the scaling factor α and thenormalizing factor β may be defined by Equation 3 below:

$\begin{matrix}\left\{ \begin{matrix}{\alpha = 10^{(\frac{{- {Injection}}\mspace{14mu} {le}\; {vel}}{20})}} \\{\beta = \frac{1}{\sqrt{1 + \alpha^{2}}}}\end{matrix} \right. & (3)\end{matrix}$

TABLE 1 EL Injection level relative to CL Scaling factor α Normalizingfactor β 3.0 dB 0.7079458 0.8161736 3.5 dB 0.6683439 0.8314061 4.0 dB0.6309573 0.8457262 4.5 dB 0.5956621 0.8591327 5.0 dB 0.56234130.8716346 5.5 dB 0.5308844 0.8832495 6.0 dB 0.5011872 0.8940022 6.5 dB0.4731513 0.9039241 7.0 dB 0.4466836 0.9130512 7.5 dB 0.42169650.9214231 8.0 dB 0.3981072 0.9290819 8.5 dB 0.3758374 0.9360712 9.0 dB0.3548134 0.9424353 9.5 dB 0.3349654 0.9482180 10.0 dB  0.31622780.9534626

That is, the power normalizer 345 corresponds to the normalizing factor,and reduces the power of the multiplexed signal by a level by which thecombiner 340 has increased the power.

In this case, each of the normalizing factor and the scaling factor maybe a rational number that is larger than 0 and smaller than 1.

In this case, the scaling factor may decrease as a reduction in powercorresponding to the injection level controller 330 becomes larger, andthe normalizing factor may increase as a reduction in powercorresponding to the injection level controller 330 becomes larger.

The power normalized signal passes through the time interleaver 350 fordistributing burst errors occurring over a channel.

In this case, the time interleaver 350 may be viewed as performinginterleaving that is applied to both the core layer signal and theenhanced layer signal. That is, the core layer and the enhanced layershare the time interleaver, thereby preventing the unnecessary use ofmemory and also reducing latency at the receiver.

Although will be described later in greater detail, the enhanced layersignal may correspond to enhanced layer data restored based oncancellation corresponding to the restoration of core layer datacorresponding to the core layer signal. The combiner 340 may combine oneor more extension layer signals having power levels lower than those ofthe core layer signal and the enhanced layer signal with the core layersignal and the enhanced layer signal.

Meanwhile, L1 signaling information including injection levelinformation is encoded by the L1 signaling generation unit 360 includingsignaling-dedicated BICM. In this case, the L1 signaling generation unit360 may receive injection level information IL INFO from the injectionlevel controller 330, and may generate an L1 signaling signal.

In L1 signaling, L1 refers to Layer-1 in the lowest layer of the ISO 7layer model. In this case, the L1 signaling may be included in apreamble.

In general, the L1 signaling may include an FFT size, a guard intervalsize, etc., i.e., the important parameters of the OFDM transmitter, achannel code rate, modulation information, etc., i.e., BICM importantparameters. This L1 signaling signal is combined with data signal into abroadcast signal frame.

The frame builder 370 generates a broadcast signal frame by combiningthe L1 signaling signal with a data signal.

Although not shown in FIG. 6, the output signal of the frame builder 370may be provided to the OFDM transmitter.

In this case, the OFDM transmitter may generate a pilot signal that isshared by the core layer and the enhanced layer.

The broadcast signal frame may be transmitted via the OFDM transmitterthat is robust to a multi-path and the Doppler phenomenon. In this case,the OFDM transmitter may be viewed as being responsible for thetransmission signal generation of the next generation broadcastingsystem.

FIG. 7 is a diagram showing an example of the structure of a broadcastsignal frame.

Referring to FIG. 7, a broadcast signal frame includes an L1 signalingsignal and a data signal. For example, the broadcast signal frame may bean ATSC 3.0 frame.

FIG. 8 is a block diagram showing another example of the signalmultiplexer shown in FIG. 1.

Referring to FIG. 8, it can be seen that a signal multiplexermultiplexes data corresponding to N (N is a natural number that is equalto or larger than 1) extension layers together in addition to core layerdata and enhanced layer data.

That is, the signal multiplexer shown in FIG. 8 includes N extensionlayer BICM units 410, . . . , 430 and injection level controllers 440, .. . , 460 in addition to a core layer BICM unit 310, an enhanced layerBICM unit 320, an injection level controller 330, a combiner 340, apower normalizer 345, a time interleaver 350, an L1 signaling generationunit 360, and a frame builder 370.

The core layer BICM unit 310, enhanced layer BICM unit 320, injectionlevel controller 330, combiner 340, power normalizer 345, timeinterleaver 350, L1 signaling generation unit 360 and frame builder 370shown in FIG. 8 have been described in detail with reference to FIG. 6.

Each of the N extension layer BICM units 410, . . . , 430 independentlyperforms BICM encoding, and each of the injection level controllers 440,. . . , 460 performs power reduction corresponding to a correspondingextension layer, thereby enabling a power reduced extension layer signalto be combined with other layer signals via the combiner 340.

In this case, each of the error correction encoders of the extensionlayer BICM units 410, . . . , 430 may be formed by connecting a BCHencoder and an LDPC encoder in series.

In particular, it is preferred that a reduction in power correspondingto each of the injection level controllers 440, . . . , 460 be higherthan the reduction in power of the injection level controller 330. Thatis, a lower one of the injection level controllers 330, 440, . . . , 460shown in FIG. 8 may correspond to a larger reduction in power.

Injection level information provided by the injection level controllers330, 440 and 460 shown in FIG. 8 is included in the broadcast signalframe of the frame builder 370 via the L1 signaling generation unit 360,and is then transmitted to the receiver. That is, the injection level ofeach layer is contained in the L1 signaling information and thentransferred to the receiver.

Although not shown in FIG. 8, the output signal of the frame builder 370may be provided to the OFDM transmitter.

In this case, the OFDM transmitter may generate a pilot signal that isshared by the core layer, the enhanced layer and the extension layer.

In the present invention, the adjustment of power may correspond toincreasing or decreasing the power of an input signal, and maycorrespond to increasing or decreasing the gain of an input signal.

The power normalizer 345 mitigates an increase in power caused by thecombination of a plurality of layer signals by means of the combiner340.

In the example shown in FIG. 8, the power normalizer 345 may adjust thepower of a signal to appropriate magnitude by multiplying the magnitudeof a signal, into which the signals of the respective layers arecombined, by a normalizing factor by using Equation 4 below:

$\begin{matrix}{{{Normalizing}\mspace{14mu} {factor}} = \left( \sqrt{\begin{pmatrix}{1 + 10^{{- {Injection}}\mspace{11mu} {level}\mspace{11mu} {\# 1}{{({d\; B})}/10}} + 10^{{- {Injection}}\mspace{14mu} {level}\; {\# 2}\; {{({d\; B})}/10}} + \ldots +} \\10^{{- {Injection}}\mspace{11mu} {level}\mspace{11mu} \# {({N + 1})}{{({d\; B})}/10}}\end{pmatrix}} \right)^{- 1}} & (4)\end{matrix}$

The time interleaver 350 performs interleaving equally applied to thesignals of the layers by interleaving the signals combined by thecombiner 340.

FIG. 9 is a block diagram showing still an example of the signaldemultiplexer shown in FIG. 1.

Referring to FIG. 9, a signal demultiplexer according to an embodimentof the present invention includes a time deinterleaver 510, ade-normalizer 1010, core layer BICM decoder 520, an enhanced layersymbol extractor 530, a de-injection level controller 1020, and anenhanced layer BICM decoder 540.

In this case, the signal demultiplexer shown in FIG. 9 may correspond tothe signal multiplexer shown in FIG. 6.

The time deinterleaver 510 may receive a received signal from the OFDMreceiver, or may receive a channel-compensated output from the channelcompensator shown in FIG. 5.

The time deinterleaver 510 receives a received signal from an OFDMreceiver for performing operations, such as time/frequencysynchronization, channel estimation and equalization, and performs anoperation related to the distribution of burst errors occurring over achannel. In this case, the L1 signaling information is decoded by theOFDM receiver first, and is then used for the decoding of data. Inparticular, the injection level information of the L1 signalinginformation may be transferred to the de-normalizer 1010 and thede-injection level controller 1020. In this case, the OFDM receiver maydecode the received signal in the form of a broadcast signal frame, forexample, an ATSC 3.0 frame, may extract the data symbol part of theframe, and may provide the extracted data symbol part to the timedeinterleaver 510. That is, the time deinterleaver 510 distributes bursterrors occurring over a channel by performing deinterleaving whilepassing a data symbol therethrough.

The de-normalizer 1010 corresponds to the power normalizer of thetransmitter, and increases power by a level by which the powernormalizer has decreased the power. That is, the de-normalizer 1010divides the received signal by the normalizing factor of Equation 2.

Although the de-normalizer 1010 is illustrated as adjusting the power ofthe output signal of the time interleaver 510 in the example shown inFIG. 9, the de-normalizer 1010 may be located before the timeinterleaver 510 so that power adjustment is performed beforeinterleaving in some embodiments.

That is, the de-normalizer 1010 may be viewed as being located before orafter the time interleaver 510 and amplifying the magnitude of a signalfor the purpose of the LLR calculation of the core layer symboldemapper.

The output of the time deinterleaver 510 (or the output of thede-normalizer 1010) is provided to the core layer BICM decoder 520, andthe core layer BICM decoder 520 restores core layer data.

In this case, the core layer BICM decoder 520 includes a core layersymbol demapper, a core layer bit deinterleaver, and a core layer errorcorrection decoder. The core layer symbol demapper calculates LLR valuesrelated to symbols, the core layer bit deinterleaver strongly mixes thecalculated LLR values with burst errors, and the core layer errorcorrection decoder corrects error occurring over a channel.

In this case, the core layer symbol demapper may calculate an LLR valuefor each bit using a predetermined constellation. In this case, theconstellation used by the core layer symbol mapper may vary depending onthe combination of the code rate and the modulation order that are usedby the transmitter.

In this case, the core layer symbol demapper may receive channel gain oran SNR estimated value from the OFDM receiver.

In this case, the core layer bit deinterleaver may performdeinterleaving on calculated LLR values on an LDPC code word basis.

In particular, the core layer error correction decoder may output onlyinformation bits, or may output all bits in which information bits havebeen mixed with parity bits. In this case, the core layer errorcorrection decoder may output only information bits as core layer data,and may output all bits in which information bits have been mixed withparity bits to the enhanced layer symbol extractor 530.

The core layer error correction decoder may be formed by connecting acore layer LDPC decoder and a core layer BCH decoder in series. That is,the input of the core layer error correction decoder may be input to thecore layer LDPC decoder, the output of the core layer LDPC decoder maybe input to the core layer BCH decoder, and the output of the core layerBCH decoder may become the output of the core layer error correctiondecoder. In this case, the LDPC decoder performs LDPC decoding, and theBCH decoder performs BCH decoding.

Furthermore, the enhanced layer error correction decoder may be formedby connecting an enhanced layer LDPC decoder and an enhanced layer BCHdecoder in series. That is, the input of the enhanced layer errorcorrection decoder may be input to the enhanced layer LDPC decoder, theoutput of the enhanced layer LDPC decoder may be input to the enhancedlayer BCH decoder, and the output of the enhanced layer BCH decoder maybecome the output of the enhanced layer error correction decoder.

The enhanced layer symbol extractor 530 may receive all bits from thecore layer error correction decoder of the core layer BICM decoder 520,may extract enhanced layer symbols from the output signal of the timedeinterleaver 510 or de-normalizer 1010. In an embodiment, the enhancedlayer symbol extractor 530 may not be provided with all bits by theerror correction decoder of the core layer BICM decoder 520, but may beprovided with LDPC information bits or BCH information bits by the errorcorrection decoder of the core layer BICM decoder 520.

In this case, the enhanced layer symbol extractor 530 includes a buffer,a subtracter, a core layer symbol mapper, and a core layer bitinterleaver. The buffer stores the output signal of the timedeinterleaver 510 or de-normalizer 1010. The core layer bit interleaverreceives the all bits (information bits+parity bits) of the core layerBICM decoder, and performs the same core layer bit interleaving as thetransmitter. The core layer symbol mapper generates core layer symbols,which are the same as the transmitter, from the interleaved signal. Thesubtracter obtains enhanced layer symbols by subtracting the outputsignal of the core layer symbol mapper from the signal stored in thebuffer, and transfers the enhanced layer symbols to the de-injectionlevel controller 1020. In particular, when LDPC information bits areprovided, the enhanced layer symbol extractor 530 may further include acore layer LDPC encoder. Furthermore, when BCH information bits areprovided, the enhanced layer symbol extractor 530 may further includenot only a core layer LDPC encoder but also a core layer BCH encoder.

In this case, the core layer LDPC encoder, core layer BCH encoder, corelayer bit interleaver and core layer symbol mapper included in theenhanced layer symbol extractor 530 may be the same as the LDPC encoder,BCH encoder, bit interleaver and symbol mapper of the core layerdescribed with reference to FIG. 6.

The de-injection level controller 1020 receives the enhanced layersymbols, and increases the power of the input signal by a level by whichthe injection level controller of the transmitter has decreased thepower. That is, the de-injection level controller 1020 amplifies theinput signal, and provides the amplified input signal to the enhancedlayer BICM decoder 540. For example, if at the transmitter, the powerused to combine the enhanced layer signal is lower than the power usedto combine the core layer signal by 3 dB, the de-injection levelcontroller 1020 functions to increase the power of the input signal by 3dB.

In this case, the de-injection level controller 1020 may be viewed asreceiving injection level information from the OFDM receiver andmultiplying an extracted enhanced layer signal by the enhanced layergain of Equation 5:

Enhanced layer gain=(√{square root over(10^(−Injectionlevel(dB)/10))})¹  (5))

The enhanced layer BICM decoder 540 receives the enhanced layer symbolwhose power has been increased by the de-injection level controller1020, and restores the enhanced layer data.

In this case, the enhanced layer BICM decoder 540 may include anenhanced layer symbol demapper, an enhanced layer bit deinterleaver, andan enhanced layer error correction decoder. The enhanced layer symboldemapper calculates LLR values related to the enhanced layer symbols,the enhanced layer bit deinterleaver strongly mixes the calculated LLRvalues with burst errors, and the enhanced layer error correctiondecoder corrects error occurring over a channel.

In this case, the enhanced layer symbol demapper may receive channelgain or an SNR estimated value from the OFDM receiver.

Although the enhanced layer BICM decoder 540 performs a task similar toa task that is performed by the core layer BICM decoder 520, theenhanced layer LDPC decoder generally performs LDPC decoding related toa code rate equal to or higher than 6/15.

For example, the core layer may use LDPC code having a code rate equalto or higher than 5/15, and the enhanced layer may use LDPC code havinga code rate equal to or higher than 6/15. In this case, in a receptionenvironment in which enhanced layer data can be decoded, core layer datamay be decoded using only a small number of LDPC decoding iterations.Using this characteristic, in the hardware of the receiver, a singleLDPC decoder is shared by the core layer and the enhanced layer, andthus the cost required to implement the hardware can be reduced. In thiscase, the core layer LDPC decoder may use only some time resources (LDPCdecoding iterations), and the enhanced layer LDPC decoder may use mosttime resources.

That is, the signal demultiplexer shown in FIG. 9 restores core layerdata first, leaves only the enhanced layer symbols by cancellation thecore layer symbols in the received signal symbols, and then restoresenhanced layer data by increasing the power of the enhanced layersymbols. As described with reference to FIGS. 5 and 6, signalscorresponding to respective layers are combined at different powerlevels, and thus data restoration having the smallest error can beachieved only if restoration starts with a signal combined with thestrongest power.

Accordingly, in the example shown in FIG. 9, the signal demultiplexermay include the time deinterleaver 510 configured to generate atime-deinterleaved signal by applying time deinterleaving to a receivedsignal; a de-normalizer 1010 configured to increase the power of thereceived signal or the time-deinterleaved signal by a levelcorresponding to a reduction in power by the power normalizer of thetransmitter; the core layer BICM decoder 520 configured to restore corelayer data from the signal power-adjusted by the de-normalizer 1010; theenhanced layer symbol extractor 530 configured to extract an enhancedlayer signal by performing cancellation, corresponding to the core layerdata, on the signal power-adjusted by the de-normalizer 1010 using theoutput signal of the core layer FEC decoder of the core layer BICMdecoder 520; a de-injection level controller 1020 configured to increasethe power of the enhanced layer signal by a level corresponding to areduction in power by the injection power level controller of thetransmitter; and an enhanced layer BICM decoder 540 configured torestore enhanced layer data using the output signal of the de-injectionlevel controller 1020.

In this case, the enhanced layer symbol extractor may receive all codewords from the core layer LDPC decoder of the core layer BICM decoder,and may immediately perform bit interleaving on the all code words.

In this case, the enhanced layer symbol extractor may receiveinformation bits from the core layer LDPC decoder of the core layer BICMdecoder, and may perform core layer LDPC encoding and then bitinterleaving on the information bits.

In this case, the enhanced layer symbol extractor may receiveinformation bits from the core layer BCH decoder of the core layer BICMdecoder, and may perform core layer BCH encoding and core layer LDPCencoding and then bit interleaving on the information bits.

In this case, the de-normalizer and the de-injection level controllermay receive injection level information IL INFO provided based on L1signaling, and may perform power control based on the injection levelinformation.

In this case, the core layer BICM decoder may correspond to a code ratelower than that of the enhanced layer BICM decoder, and may be morerobust than the enhanced layer BICM decoder.

In this case, the de-normalizer may correspond to the reciprocal of thenormalizing factor.

In this case, the de-injection level controller may correspond to thereciprocal of the scaling factor.

In this case, the enhanced layer data may be restored based oncancellation corresponding to the restoration of core layer datacorresponding to the core layer signal.

In this case, the signal demultiplexer further may include one or moreextension layer symbol extractors each configured to extract anextension layer signal by performing cancellation corresponding toprevious layer data; one or more de-injection level controllers eachconfigured to increase the power of the extension layer signal by alevel corresponding to a reduction in power by the injection levelcontroller of the transmitter; and one or more extension layer BICMdecoders configured to restore one or more pieces of extension layerdata using the output signals of the one or more de-injection levelcontrollers.

From the configuration shown in FIG. 9, it can be seen that a signaldemultiplexing method according to an embodiment of the presentinvention includes generating a time-deinterleaved signal by applyingtime deinterleaving to a received signal; increasing the power of thereceived signal or the time-deinterleaved signal by a levelcorresponding to a reduction in power by the power normalizer of thetransmitter; restoring core layer data from the power-adjusted signal;extracting an enhanced layer signal by performing cancellation,corresponding to the core layer data, on the power-adjusted signal;increasing the power of the enhanced layer signal by a levelcorresponding to a reduction in power by the injection power levelcontroller of the transmitter; and restoring enhanced layer data usingthe enhanced layer data.

In this case, extracting the enhanced layer signal may include receivingall code words from the core layer LDPC decoder of the core layer BICMdecoder, and immediately performing bit interleaving on the all codewords.

In this case, extracting the enhanced layer signal may include receivinginformation bits from the core layer LDPC decoder of the core layer BICMdecoder, and performing core layer LDPC encoding and then bitinterleaving on the information bits.

In this case, extracting the enhanced layer signal may include receivinginformation bits from the core layer BCH decoder of the core layer BICMdecoder, and performing core layer BCH encoding and core layer LDPCencoding and then bit interleaving on the information bits.

FIG. 10 is a block diagram showing an example of the core layer BICMdecoder 520 and the enhanced layer symbol extractor 530 shown in FIG. 9.

Referring to FIG. 10, the core layer BICM decoder 520 includes a corelayer symbol demapper, a core layer bit deinterleaver, a core layer LDPCdecoder, and a core layer BCH decoder.

That is, in the example shown in FIG. 10, the core layer errorcorrection decoder includes the core layer LDPC decoder and the corelayer BCH decoder.

Furthermore, in the example shown in FIG. 10, the core layer LDPCdecoder provides all code words, including parity bits, to the enhancedlayer symbol extractor 530. That is, although the LDPC decoder generallyoutputs only the information bits of all the LDPC code words, the LDPCdecoder may output all the code words.

In this case, although the enhanced layer symbol extractor 530 may beeasily implemented because it does not need to include a core layer LDPCencoder or a core layer BCH encoder, there is a possibility that aresidual error may remain in the LDPC code parity part.

FIG. 11 is a block diagram showing another example of the core layerBICM decoder 520 and the enhanced layer symbol extractor 530 shown inFIG. 9.

Referring to FIG. 11, the core layer BICM decoder 520 includes a corelayer symbol demapper, a core layer bit deinterleaver, a core layer LDPCdecoder, and a core layer BCH decoder.

That is, in the example shown in FIG. 11, the core layer errorcorrection decoder includes the core layer LDPC decoder and the corelayer BCH decoder.

Furthermore, in the example shown in FIG. 11, the core layer LDPCdecoder provides information bits, excluding parity bits, to theenhanced layer symbol extractor 530.

In this case, although the enhanced layer symbol extractor 530 does notneed to include a core layer BCH encoder, it must include a core layerLDPC encoder.

A residual error that may remain in the LDPC code parity part may beeliminated more desirably in the example shown in FIG. 11 than in theexample shown in FIG. 10.

FIG. 12 is a block diagram showing still another example of the corelayer BICM decoder 520 and the enhanced layer symbol extractor 530 shownin FIG. 9.

Referring to FIG. 12, the core layer BICM decoder 520 includes a corelayer symbol demapper, a core layer bit deinterleaver, a core layer LDPCdecoder, and a core layer BCH decoder.

That is, in the example shown in FIG. 12, the core layer errorcorrection decoder includes the core layer LDPC decoder and the corelayer BCH decoder.

In the example shown in FIG. 12, the output of the core layer BCHdecoder corresponding to core layer data is provided to the enhancedlayer symbol extractor 530.

In this case, although the enhanced layer symbol extractor 530 has highcomplexity because it must include both a core layer LDPC encoder and acore layer BCH encoder, it guarantees higher performance than those inthe examples of FIGS. 10 and 11.

FIG. 13 is a block diagram showing another example of the signaldemultiplexer shown in FIG. 1.

Referring to FIG. 13, a signal demultiplexer according to an embodimentof the present invention includes a time deinterleaver 510, ade-normalizer 1010, a core layer BICM decoder 520, an enhanced layersymbol extractor 530, an enhanced layer BICM decoder 540, one or moreextension layer symbol extractors 650 and 670, one or more extensionlayer BICM decoders 660 and 680, and de-injection level controllers1020, 1150 and 1170.

In this case, the signal demultiplexer shown in FIG. 13 may correspondto the signal multiplexer shown in FIG. 8.

The time deinterleaver 510 may receive a received signal from an OFDMreceiver, and may receive a channel-compensated output from the channelcompensator shown in FIG. 5.

The time deinterleaver 510 receives a received signal from an OFDMreceiver for performing operations, such as synchronization, channelestimation and equalization, and performs an operation related to thedistribution of burst errors occurring over a channel. In this case, L1signaling information may be decoded by the OFDM receiver first, andthen may be used for data decoding. In particular, the injection levelinformation of the L1 signaling information may be transferred to thede-normalizer 1010 and the de-injection level controllers 1020, 1150 and1170.

In this case, the de-normalizer 1010 may obtain the injection levelinformation of all layers, may obtain a de-normalizing factor usingEquation 6 below, and may multiply the input signal with thede-normalizing factor:

$\begin{matrix}{{{De}\text{-}{normalizing}\mspace{14mu} {factor}} = {\left( {{normalizing}\mspace{14mu} {factor}} \right)^{- 1} = \left( \sqrt{\begin{pmatrix}{1 + 10^{{- {Injection}}\mspace{11mu} {level}\mspace{11mu} {\# 1}{{({d\; B})}/10}} + 10^{{- {Injection}}\mspace{14mu} {level}\; {\# 2}\; {{({d\; B})}/10}} + \ldots +} \\10^{{- {Injection}}\mspace{11mu} {level}\mspace{11mu} \# {({N + 1})}{{({d\; B})}/10}}\end{pmatrix}} \right)^{- 1}}} & (6)\end{matrix}$

That is, the de-normalizing factor is the reciprocal of the normalizingfactor expressed by Equation 4 above.

In an embodiment, when the N1 signaling includes not only injectionlevel information but also normalizing factor information, thede-normalizer 1010 may simply obtain a de-normalizing factor by takingthe reciprocal of a normalizing factor without the need to calculate thede-normalizing factor using an injection level.

The de-normalizer 1010 corresponds to the power normalizer of thetransmitter, and increases power by a level by which the powernormalizer has decreased the power.

Although the de-normalizer 1010 is illustrated as adjusting the power ofthe output signal of the time interleaver 510 in the example shown inFIG. 13, the de-normalizer 1010 may be located before the timeinterleaver 510 so that power adjustment can be performed beforeinterleaving in an embodiment.

That is, the de-normalizer 1010 may be viewed as being located before orafter the time interleaver 510 and amplifying the magnitude of a signalfor the purpose of the LLR calculation of the core layer symboldemapper.

The output of the time deinterleaver 510 (or the output of thede-normalizer 1010) is provided to the core layer BICM decoder 520, andthe core layer BICM decoder 520 restores core layer data.

In this case, the core layer BICM decoder 520 includes a core layersymbol demapper, a core layer bit deinterleaver, and a core layer errorcorrection decoder. The core layer symbol demapper calculates LLR valuesrelated to symbols, the core layer bit deinterleaver strongly mixes thecalculated LLR values with burst errors, and the core layer errorcorrection decoder corrects error occurring over a channel.

In this case, the core layer symbol demapper may receive channel gain oran SNR estimated value from the OFDM receiver.

In particular, the core layer error correction decoder may output onlyinformation bits, or may output all bits in which information bits havebeen combined with parity bits. In this case, the core layer errorcorrection decoder may output only information bits as core layer data,and may output all bits in which information bits have been combinedwith parity bits to the enhanced layer symbol extractor 530.

The core layer error correction decoder may be formed by connecting acore layer LDPC decoder and a core layer BCH decoder in series. That is,the input of the core layer error correction decoder may be input to thecore layer LDPC decoder, the output of the core layer LDPC decoder maybe input to the core layer BCH decoder, and the output of the core layerBCH decoder may become the output of the core layer error correctiondecoder. In this case, the LDPC decoder performs LDPC decoding, and theBCH decoder performs BCH decoding.

The enhanced layer error correction decoder may be also formed byconnecting an enhanced layer LDPC decoder and an enhanced layer BCHdecoder in series. That is, the input of the enhanced layer errorcorrection decoder may be input to the enhanced layer LDPC decoder, theoutput of the enhanced layer LDPC decoder may be input to the enhancedlayer BCH decoder, and the output of the enhanced layer BCH decoder maybecomes the output of the enhanced layer error correction decoder.

Moreover, the extension layer error correction decoder may be alsoformed by connecting an extension layer LDPC decoder and an extensionlayer BCH decoder in series. That is, the input of the extension layererror correction decoder may be input to the extension layer LDPCdecoder, the output of the extension layer LDPC decoder may be input tothe extension layer BCH decoder, and the output of the extension layerBCH decoder may becomes the output of the extension layer errorcorrection decoder.

In particular, the tradeoff between the complexity of implementation,regarding which of the outputs of the error correction decoders will beused, which has been described with reference to FIGS. 10, 11 and 12,and performance is applied to not only the core layer BICM decoder 520and enhanced layer symbol extractor 530 of FIG. 13 but also theextension layer symbol extractors 650 and 670 and the extension layerBICM decoders 660 and 680.

The enhanced layer symbol extractor 530 may receive the all bits fromthe core layer BICM decoder 520 of the core layer error correctiondecoder, and may extract enhanced layer symbols from the output signalof the time deinterleaver 510 or the denormalizer 1010. In anembodiment, the enhanced layer symbol extractor 530 may not receive allbits from the error correction decoder of the core layer BICM decoder520, but may receive LDPC information bits or BCH information bits.

In this case, the enhanced layer symbol extractor 530 includes a buffer,a subtracter, a core layer symbol mapper, and a core layer bitinterleaver. The buffer stores the output signal of the timedeinterleaver 510 or de-normalizer 1010. The core layer bit interleaverreceives the all bits (information bits+parity bits) of the core layerBICM decoder, and performs the same core layer bit interleaving as thetransmitter. The core layer symbol mapper generates core layer symbols,which are the same as the transmitter, from the interleaved signal. Thesubtracter obtains enhanced layer symbols by subtracting the outputsignal of the core layer symbol mapper from the signal stored in thebuffer, and transfers the enhanced layer symbols to the de-injectionlevel controller 1020.

In this case, the core layer bit interleaver and core layer symbolmapper included in the enhanced layer symbol extractor 530 may be thesame as the core layer bit interleaver and the core layer symbol mappershown in FIG. 8.

The de-injection level controller 1020 receives the enhanced layersymbols, and increases the power of the input signal by a level by whichthe injection level controller of the transmitter has decreased thepower. That is, the de-injection level controller 1020 amplifies theinput signal, and provides the amplified input signal to the enhancedlayer BICM decoder 540.

The enhanced layer BICM decoder 540 receives the enhanced layer symbolwhose power has been increased by the de-injection level controller1020, and restores the enhanced layer data.

In this case, the enhanced layer BICM decoder 540 may include anenhanced layer symbol demapper, an enhanced layer bit deinterleaver, andan enhanced layer error correction decoder. The enhanced layer symboldemapper calculates LLR values related to the enhanced layer symbols,the enhanced layer bit deinterleaver strongly mixes the calculated LLRvalues with burst errors, and the enhanced layer error correctiondecoder corrects error occurring over a channel.

In this case, the enhanced layer symbol demapper may receive channelgain or an SNR estimated value from the OFDM receiver.

In particular, the enhanced layer error correction decoder may outputonly information bits, and may output all bits in which information bitshave been combined with parity bits. In this case, the enhanced layererror correction decoder may output only information bits as enhancedlayer data, and may output all bits in which information bits have beenmixed with parity bits to the extension layer symbol extractor 650.

The extension layer symbol extractor 650 receives all bits from theenhanced layer error correction decoder of the enhanced layer BICMdecoder 540, and extracts extension layer symbols from the output signalof the de-injection level controller 1020.

In this case, the de-injection level controller 1020 may amplify thepower of the output signal of the subtracter of the enhanced layersymbol extractor 530.

In this case, the extension layer symbol extractor 650 includes abuffer, a subtracter, an enhanced layer symbol mapper, and an enhancedlayer bit interleaver. The buffer stores the output signal of thede-injection level controller 1020. The enhanced layer bit interleaverreceives the all bits information (bits+parity bits) of the enhancedlayer BICM decoder, and performs enhanced layer bit interleaving that isthe same as that of the transmitter. The enhanced layer symbol mappergenerates enhanced layer symbols, which are the same as those of thetransmitter, from the interleaved signal. The subtracter obtainsextension layer symbols by subtracting the output signal of the enhancedlayer symbol mapper from the signal stored in the buffer, and transfersthe extension layer symbols to the extension layer BICM decoder 660.

In this case, the enhanced layer bit interleaver and the enhanced layersymbol mapper included in the extension layer symbol extractor 650 maybe the same as the enhanced layer bit interleaver and the enhanced layersymbol mapper shown in FIG. 8.

The de-injection level controller 1150 increases power by a level bywhich the injection level controller of a corresponding layer hasdecreased the power at the transmitter.

In this case, the de-injection level controller may be viewed asperforming the operation of multiplying the extension layer gain ofEquation 7 below. In this case, a 0-th injection level may be consideredto be 0 dB:

$\begin{matrix}{{n\text{-}{th}\mspace{14mu} {extension}\mspace{14mu} {layer}\mspace{14mu} {gain}} = \frac{10^{{- {Injection}}\mspace{11mu} {level}\mspace{11mu} \# {({n - 1})}{{({d\; B})}/10}}}{10^{{- {Injection}}\mspace{11mu} {level}\mspace{11mu} \# n\; {{({d\; B})}/10}}}} & (7)\end{matrix}$

The extension layer BICM decoder 660 receives the extension layersymbols whose power has been increased by the de-injection levelcontroller 1150, and restores extension layer data.

In this case, the extension layer BICM decoder 660 may include anextension layer symbol demapper, an extension layer bit deinterleaver,and an extension layer error correction decoder. The extension layersymbol demapper calculates LLR values related to the extension layersymbols, the extension layer bit deinterleaver strongly mixes thecalculated LLR values with burst errors, and the extension layer errorcorrection decoder corrects error occurring over a channel.

In this case, the extension layer symbol demapper may receive channelgain or an SNR estimated value from the OFDM receiver.

In particular, each of the extension layer symbol extractor and theextension layer BICM decoder may include two or more extractors ordecoders if two or more extension layers are present.

That is, in the example shown in FIG. 13, the extension layer errorcorrection decoder of the extension layer BICM decoder 660 may outputonly information bits, and may output all bits in which information bitshave been combined with parity bits. In this case, the extension layererror correction decoder outputs only information bits as extensionlayer data, and may output all bits in which information bits have beenmixed with parity bits to the subsequent extension layer symbolextractor 670.

The configuration and operation of the extension layer symbol extractor670, the extension layer BICM decoder 680 and the de-injection levelcontroller 1170 can be easily understood from the configuration andoperation of the above-described extension layer symbol extractor 650,extension layer BICM decoder 660 and de-injection level controller 1150.

A lower one of the de-injection level controllers 1020, 1150 and 1170shown in FIG. 13 may correspond to a larger increase in power. That is,the de-injection level controller 1150 may increase power more than thede-injection level controller 1020, and the de-injection levelcontroller 1170 may increase power more than the de-injection levelcontroller 1150.

It can be seen that the signal demultiplexer shown in FIG. 13 restorescore layer data first, restores enhanced layer data using thecancellation of core layer symbols, and restores extension layer datausing the cancellation of enhanced layer symbols. Two or more extensionlayers may be provided, in which case restoration starts with anextension layer combined at a higher power level.

FIG. 14 is a diagram showing in an increase in power attributable to thecombination of a core layer signal and an enhanced layer signal.

Referring to FIG. 14, it can be seen that when a multiplexed signal isgenerated by combining a core layer signal with an enhanced layer signalwhose power has been reduced by an injection level, the power level ofthe multiplexed signal is higher than the power level of the core layersignal or the enhanced layer signal.

In this case, the injection level that is adjusted by the injectionlevel controllers shown in FIGS. 6 and 8 may be adjusted from 3.0 dB to10.0 dB in steps of 0.5 dB. When the injection level is 3.0 dB, thepower of the enhanced layer signal is lower than that of the core layersignal by 3 dB. When the injection level is 10.0 dB, the power of theenhanced layer signal is lower than that of the core layer signal by 10dB. This relationship may be applied not only between a core layersignal and an enhanced layer signal but also between an enhanced layersignal and an extension layer signal or between extension layer signals.

The power normalizers shown in FIGS. 6 and 8 may adjust the power levelafter the combination, thereby solving problems, such as the distortionof the signal, that may be caused by an increase in power attributableto the combination.

FIG. 15 is an operation flowchart showing a signal multiplexing methodaccording to an embodiment of the present invention.

Referring to FIG. 15, in the signal multiplexing method according to theembodiment of the present invention, BICM is applied to core layer dataat step S1210.

Furthermore, in the signal multiplexing method according to theembodiment of the present invention, BICM is applied to enhanced layerdata at step S1220.

The BICM applied at step S1220 may be different from the BICM applied tostep S1210. In this case, the BICM applied at step S1220 may be lessrobust than the BICM applied to step S1210. In this case, the bit rateof the BICM applied at step S1220 may be less robust than that of theBICM applied to step S1210.

In this case, an enhanced layer signal may correspond to the enhancedlayer data that is restored based on cancellation corresponding to therestoration of the core layer data corresponding to a core layer signal.

Furthermore, in the signal multiplexing method according to theembodiment of the present invention, a power-reduced enhanced layersignal is generated by reducing the power of the enhanced layer signalat step S1230.

In this case, at step S1230, an injection level may be changed from 3.0dB to 10.0 dB in steps of 0.5 dB.

Furthermore, in the signal multiplexing method according to theembodiment of the present invention, a multiplexed signal is generatedby combining the core layer signal and the power-reduced enhanced layersignal at step S1240.

That is, at step S1240, the core layer signal and the enhanced layersignal are combined at different power levels so that the power level ofthe enhanced layer signal is lower than the power level of the corelayer signal.

In this case, at step S1240, one or more extension layer signals havinglower power levels than the core layer signal and the enhanced layersignal may b e combined with the core layer signal and the enhancedlayer signal.

Furthermore, in the signal multiplexing method according to theembodiment of the present invention, the power of the multiplexed signalis reduced at step S1250.

In this case, at step S1250, the power of the multiplexed signal may bereduced to the power of the core layer signal. In this case, at stepS1250, the power of the multiplexed signal may be reduced by a level bywhich the power has been increased at step S1240.

Furthermore, in the signal multiplexing method according to theembodiment of the present invention, a time-interleaved signal isgenerated by performing time interleaving that is applied to both thecore layer signal and the enhanced layer signal is performed at stepS1260.

Furthermore, in the signal multiplexing method according to theembodiment of the present invention, a broadcast signal frame isgenerated using the time-interleaved signal and L1 signaling informationat step S1270.

In this case, a core layer corresponding to the core layer signal and anenhanced layer corresponding to the enhanced layer signal may share apilot signal that is generated by the OFDM transmitter.

In this case, the broadcast signal frame may be an ATSC 3.0 frame.

In this case, the L1 signaling information may include injection levelinformation and/or normalizing factor information.

Although not explicitly shown in FIG. 15, the signal multiplexing methodmay further include the step of generating L1 signaling informationincluding injection level information corresponding to step S1230.

The signal multiplexing method shown in FIG. 15 may correspond to stepS210 shown in FIG. 2.

As described above, the signal multiplexing apparatus and methodaccording to the present invention are not limited to the configurationsand methods of the aforemtioned embodiments, but some or all of theembodiments may be selectively combined such that the embodiments aremodified in various manners.

1. A broadcast signal transmission apparatus, comprising: a combinerconfigured to generate a multiplexed signal by combining a core layersignal and an enhanced layer signal at different power levels; a powernormalizer configured to reduce power of the multiplexed signal to apower level corresponding to the core layer signal; a time interleaverconfigured to generate a time-interleaved signal by performinginterleaving that is applied to both the core layer signal and theenhanced layer signal; a frame builder configured to generate abroadcast signal frame using the time-interleaved signal; and anorthogonal frequency division multiplexing (OFDM) transmitter configuredto generate a pilot signal that is shared by a core layer correspondingto the core layer signal and an enhanced layer corresponding to theenhanced layer signal.
 2. The broadcast signal transmission apparatus ofclaim 1, further comprising an injection level controller configured togenerate a power-reduced enhanced layer signal by reducing power of theenhanced layer signal; and wherein the combiner generates themultiplexed signal by combining the core layer signal and thepower-reduced enhanced layer signal.
 3. The broadcast signaltransmission apparatus of claim 2, further comprising an L1 signalinggeneration unit configured to generate L1 signaling informationincluding injection level information of the injection level controller.4. The broadcast signal transmission apparatus of claim 3, furthercomprising: a core layer Bit-Interleaved Coded Modulation (BICM) unitconfigured to correspond to the core layer signal; and an enhanced layerBICM unit configured to perform Bit-Interleaved Coded Modulation (BICM)encoding different from that of the core layer BICM unit.
 5. Thebroadcast signal transmission apparatus of claim 4, wherein the corelayer BICM unit has a lower bit rate than the enhanced layer BICM unit,and is more robust than the enhanced layer BICM unit.
 6. The broadcastsignal transmission apparatus of claim 3, wherein the power normalizercorresponds to a normalizing factor, and reduces the power of themultiplexed signal by a level by which the power has been increased bythe combiner.
 7. The broadcast signal transmission apparatus of claim 6,wherein: the injection level controller corresponds to a scaling factor;each of the normalizing factor and the scaling factor is a value that islarger than 0 and smaller than 1; the scaling factor decreases as areduction in power corresponding to the injection level controllerbecomes larger; and the normalizing factor increases as a reduction inpower corresponding to the injection level controller becomes larger. 8.The broadcast signal transmission apparatus of claim 3, wherein theinjection level controller changes an injection level between 3.0 dB and10.0 dB in steps of 0.5 dB.
 9. The broadcast signal transmissionapparatus of claim 3, wherein the enhanced layer signal corresponds toenhanced layer data that is restored based on cancellation correspondingto restoration of core layer data corresponding to the core layersignal.
 10. The broadcast signal transmission apparatus of claim 9,wherein the core layer BICM unit comprises: a core layer errorcorrection encoder configured to perform error correction encoding onthe core layer data; a core layer bit interleaver configured to performbit interleaving corresponding to the core layer data; and a core layersymbol mapper configured to perform modulation corresponding to the corelayer data.
 11. The broadcast signal transmission apparatus of claim 10,wherein the enhanced layer BICM unit comprises: an enhanced layer errorcorrection encoder configured to perform error correction encoding onthe enhanced layer data; an enhanced layer bit interleaver configured toperform bit interleaving corresponding to the enhanced layer data; andan enhanced layer symbol mapper configured to perform modulationcorresponding to the enhanced layer data.
 12. The broadcast signaltransmission apparatus of claim 11, wherein: a combination of theenhanced layer error correction encoder and the enhanced layer symbolmapper is less robust than a combination of the core layer errorcorrection encoder and the core layer symbol mapper.
 13. The broadcastsignal transmission apparatus of claim 12, wherein the combiner combinesone or more extension layer signals, having lower power levels than thecore layer signal and the enhanced layer signal, with the core layersignal and the enhanced layer signal.
 14. A broadcast signaltransmission method, comprising: generating a multiplexed signal bycombining a core layer signal and an enhanced layer signal at differentpower levels; reducing power of the multiplexed signal to a power levelcorresponding to the core layer signal; generating a time-interleavedsignal by performing interleaving that is applied to both the core layersignal and the enhanced layer signal; generating a broadcast signalframe using the time-interleaved signal; and generating a pilot signalthat is shared by a core layer corresponding to the core layer signaland an enhanced layer corresponding to the enhanced layer signal. 15.The broadcast signal transmission method of claim 14, further comprisinggenerating a power-reduced enhanced layer signal by reducing power ofthe enhanced layer signal; and wherein the combining comprisesgenerating a multiplexed signal by combining the core layer signal andthe power-reduced enhanced layer signal.
 16. The broadcast signaltransmission method of claim 15, further comprising generating L1signaling information including injection level information.
 17. Thebroadcast signal transmission method of claim 15, wherein the reducingpower of the multiplexed signal comprises reducing the power of themultiplexed signal by a level by which the power has been increased bythe combining.
 18. The broadcast signal transmission method of claim 17,wherein the generating a power-reduced enhanced layer signal compriseschanging an injection level between 3.0 dB and 10.0 dB in steps of 0.5dB.
 19. The broadcast signal transmission method of claim 18, whereinthe enhanced layer signal corresponds to enhanced layer data that isrestored based on cancellation corresponding to restoration of corelayer data corresponding to the core layer signal.
 20. The broadcastsignal transmission method of claim 18, wherein the combining comprisescombining one or more extension layer signals, having lower power levelsthan the core layer signal and the enhanced layer signal, with the corelayer signal and the enhanced layer signal.